Fuel injection apparatus

ABSTRACT

In a fuel injection apparatus a fuel metering valve is controlled by an air sensor disposed in the air intake tube of an internal combustion engine for metering fuel quantities that are proportionate to the intake air quantities. The pressure difference across the fuel metering valve is varied as a function of at least one engine variable in a hysteresis-free manner by means of an electromagnetic system including a coil armature and a permanent magnet.

United States Patent 1191 lt apeet 1 51 May 7, 1974 [5 FUEL INJECTION APPARATUS 3,728,993 4/1973 ECkelI et al. 123/119 R 3,783,341 6/1973 LOOS [75] lnvemors- Hemnch Knapp 3,739,758 6/1973 Knapp et a1 123/139 AW LeoHaFFg-Silbrberg; Reinhard Schwartz, Stuttgart, both of Germany 73 Assignee: Robert Bosch GmbH, Stuttgart,

Germany [22] Filed: Jan. 22, 1973 21 Appl. N6; 325,743

[30] Foreign Application Priority Data Jan. 22, 1972 Germany 2203018 [52] US. CL. 123/119 R, 123/32 EA, 123/139 AW, 261/50 A Int. Cl. F02m 69/00 Field of Search 123/32 AB, 32 EA, 139 AW, 123/119 R; 261/50 A [5 6] References Cited UNITED STATES PATENTS 3,703,888 11/1928 Eckert et a1 123/139 AW X Primary Examiner-Wendell E. Burns Attorney, Agent, or Firm- Edwin E. Greigg [5 7] ABSTRACT In a fuel injection apparatus a fuel metering valve is controlled by an air sensor disposed in the air intake tube of an internal combustion engine for metering fuel quantities that are proportionate to the intake air quantities. The pressure difference across the fuel metering valve is varied as a function of at least one engine variable in a hysteresis-free manner by means of an electromagnetic system including a coil armature and a permanent magnet.

5 Claims, 2 Drawing Figures FUEL INJECTION APPARATUS BACKGROUND OF THE INVENTION This invention relates to a fuel injection apparatus for a spark plug-ignited internal combustion engine that operates on fuel continuously injected into the suction pipe in which there is disposed an arbitrarily operable butterfly valve. The fuel injection apparatus is of the type which has an 'air sensor disposed in the suction pipe spaced from the butterfly valve and is moved against a return force by and in response to the throughgoing air quantities. The motion of the air sensor is transmitted to a movable member of a fuel metering valve which is disposed in the fuel line and which meters fuel quantities that are proportionate to The air quantities flowing through the suction pipe. The fuel metering is effected under a constant pressure difference which is altered as a function of engine variables.

In a known fuel injection apparatus of the aforeoutlined type (such as disclosed, for example, in German Patent No. l,2l2,780), the pressure difference across the fuel metering valve is variable stepwise as a function of the position of the accelerator. Stated differently, the pressure difference is variable as a function of the load. The ever-increasing legal requirements regarding the components of the exhaust gas make necessary a very accurate regulation of the optimal injected fuel quantities. Thus, for example, the catalyzers used for exhaust gas purification require for the practically complete conversion of the harmful components in the exhaust gas into harmless compositions and air-fuel ratio A that is close to l.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved fuel injection apparatus in which the closed loop feedback of the signals characterizing the engine variables is effected substantially in an error-free manner.

Briefly stated, according to the invention, the pressure difference across thee fuel metering valve is variable by means of a'hysteresis-free electromagnetic system having a permanent magnet and a movable coil armature.

The invention will be better understood, as well as further objects and advantages will become more apparent, from the ensuing detailed specification of two exemplary embodiments taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic representation of a first embodiment of the invention and FIG. 2 is a schematic representation of a second embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS Turning now to FIG. 1, in the fuel injection apparatus illustrated therein the combustion air flows in the direction of the arrow into a suction tube portion 1 which is joined by a conical portion 2 accomodating an air sensor 3. Subsequent to the conical suction tube portion 2 the air flows through a connecting hose 4 and then into a suction tube portion 5 in which there is located an arbitrarily operable butterfly valve 6. Therefrom the air flows to one or more cylinders (not shown) of the internal combustion engine (also not shown). The air sensor is constituted by a plate 3 which is arranged normal to the direction of air flow and which is movable in the conical tube portion 2 as an approximately linear function of the air quantities flowing therethrough. In case of a constant return force exerted on the air sensor 3 and in case of a constant air pressure prevailing upstream of the air sensor 3, the pressure that prevails between the air sensor 3 and the butterfly valve 6 is also constant.

The air sensor 3 directly controls a fuel metering valve 7. For transmitting the displacement of the air sensor 3 to the fuel metering valve 7 there is provided a lever 8 which carries the airsensor plate 3 and which is pivotably held at the low-friction joint 9. The lever 8 is provided with an integral lug 10 which actuates the movable valve member 11 of the fuel metering valve 7. The movable valve member 11 is formed as a control plunger.

Fuel supply is efi'ected by means of a fuel pump (not shown) which drives fuel through a conduitl4 and directs ot to the fuel metering valve 7. From the conduit 14 there extends a conduit 15 containing a pressure limiting valve 16 which, in case of an excessive fuel pressure in the system, causes the fuel to flow back into the fuel tank 17.

The control plunger 11 is exposed to pressurized liquid through a conduit 20 provided with a throttle 21. The pressurized liquid serves as a return force affecting the air sensor 3.

The metering at the fuel metering valve 7 is effected at a constant pressure drop by means of a differential pressure valve 23 which is formed as a flat seat valve having a stationary valve seat 24 and a movable valve member constituted by a diaphragm 25 separating two chambers 26 and 27 from one another. The chamber 26 is in communication with the fuel metering valve 7 through a conduit 28. From the chamber 26 the metered fuel is admitted through a channel 29 in the direction of the arrow 30 to a quantity distributor (not shown) which distributes the fuel quantities uniformly among the individual fuel injection valves disposed in the suction tube in the vicinity of each engine cylinder. The differential pressure valve 23 is loaded by a spring 31 in the direction of opening. In the chamber 27 there prevails the fuel pressure upstream of the metering location. This pressure is admitted to the chamber 27 by a conduit 32. In the chamber 27 there is disposed an electromagnetic system 34 which comprises an armature 35, a solenoid 36 wound thereon, a soft iron core 37, a permanent magnet 38 and a soft iron plate 39. The latter is provided with a core 40 which extends into the solenoid armature 35 suspended friction-free by means of a leaf spring (spider) 41. The leaf spring 41 and the diaphragm 25 are coupled to one another by means of an intermediate component 42. The solenoid 36 may advantageously be energized by a circuit constructed as illustrated in FIG. 2 of the drawing accompanying and forming a part of the patent application of Knapp entitled Fuel Injection Apparatus, Ser. No. 322,382, filed on Jan. 10, 1973, and assigned to the same assignee as the present application.

The fuel injection apparatus described hereinabove operates as follows:

When the internal combustion engine is running, air is drawn through the suction tube 1, 4, 5, and, as a result, the air sensor 3 executes a certain excursion from its position of rest. As a function of the excursion of the air sensor 3, the control plunger 1 1 of the fuel metering valve 7 is shifted by the lever 8. In this manner the control plunger 11 throttles the fuel flow in the conduit 14,

28 to a greater or lesser extent. The direct coupling between the air sensor 3 and the control plunger 11 results in a constant ratio of the air quantities to the metered fuel quantities. I

For maintaining a richer or leaner fuel-air mixture as a function of the particular range in which the engine momentarily operates, a change of the pressure drop across the fuel metering valve 7 has to be effected as a function of engine variables such as, for example, the oxygen content in the exhaust gas. For this purpose there is provided an oxygen sonde which is located in the exhaust line of the internal combustion engine and which varies the energizing current flowing through the solenoid 36 of the electromagnet system 34 by means of anelectronic circuit, such as the circuit disclosed in FIG. 2 of the aforementioned application of Knapp,

filed on Jan. 9, 1973. In this manner the solenoid armature 35 is drawn to a greater or lesser extent by the magnetic force towards the core 40, that is, in the direction of a slackening of the spring 31. The quantity of the metered fuel can thus be altered by changing the differential pressure across the metering valve 7. The closed loop feedback of the control signals characterizing the engine variable can thus be effected in a hysteresis-free manner by the particular design of the electromagnetic system 34 having a solenoid armature 35 and a permanent magnet 38. The differential pressure valve 23 serves as a servo-control for an afterconnected fuel quantity distributor (not shown).

Turning now to FIG. 2, the fuel injection apparatus illustrated therein comprises a fuel metering and distributor valve 50, to which fuel is admitted from a conduit 14 through a channel 51. From the latter fuel is admitted into an annular groove 52 of the control plunger 1 1. Dependent upon the position of the control plunger 1 1, its annular groove 52 overlaps to a greater or lesser extent the control slots 53, each of which leads to a separate chamber 55 through an associated channel 54. Each chamber 55 is separated from an associated, separate chamber 57 by means of a diaphragm 56. From the chambers 55 the fuel is admitted through channels 58 to the individual fuel injection valves (not shown) which; are disposed in the engine suction tube in the vicinity of the associated engine cylinder. The diaphragm 56 serves as the movable member of flat seat valves serving as second differential pressure valves. From the fuel conduit 14 there extends a conduit 60 which is provided with a throttle 61 and which leads to the chambers 57 of the individual second differential pressure valves. The fuel pressure in the chambers 57 is variable by means of the differential pressure valve 23 over the conduit 28. From the chamber 26 of the differential pressure valve 23 the fuel may flow, in the open position of the valve, through the channel 29 back into the fuel tank 17. I

The mode of operation of the fuel injection apparatus illustrated in FIG. 2 corresponds in essence to that of the fuel injection apparatus described in connection with FIG. 1. The pressure drop through the differential pressure valve 23 variable by the electromagnetic system 34 as a function of, for example, the oxygen content in the exhaust gas in the internal combustion engine, modifies the differential pressure at the second differential pressure valves 59. Since the electromagnetic system 34 operates in a hysteresis-free manner and since in the ydraulic circuit there are no components that may be affected by hysteresis, the closed loop feedback of the signals characterizing the engine variable is effected in an error-free manner. That is, even if the air sensor 3 is in an error-prone position, the readjustment is effected by the signal of the oxygen sonde in such a manner that the fuel readjustment occurs in an error-free manner to a A value which is close to I. This makes it possible to lower the requirements pertaining to the air sensor 3 and thus the latter may be of a cheaper construction and of smaller dimensions. The air sensor 3 then overtakes in essence the preselection during transition from one operational range of the engine to the other.

What is claimed is:

1. In a fuel injection apparatus serving a spark plugignited internal combustion engine operating on fuel continuously injected into the engine suction pipe containing an arbitrarily operable butterfly valve, said apparatus being of the type that has (a) a fuel metering valve including a movable valve member disposed in the fuel line of the engine, (b) an air sensor disposed in said suction pipe spaced from said butterfly valve, said air sensor being deflected by and as a function of the air quantities flowing through said suction pipe, (c) means for exerting a return force on said air sensor, (d) means for connecting said air sensor to said movable valve member to displace the latter for metering a fuel quantity that is proportionate to the air quantities, said fuel metering being effected at a constant pressure difference across said fuel metering valve, said pressure difference being alterable as a function of at least one engine variable, the improvement comprising a hysteresis-free electromagnetic system operatively connected to said fuel metering valve, said electromagnetic system including a permanent magnet and a movable coil armature for varying said pressure difference.

2. An improvement as defined in claim 1, including a differential pressure valve formed as a flat seat valve having a movable valve member constituted by a diaphragm, a spring means engaging said diaphragm and urging the latter in'the opening direction of said differential pressure valve, said movable coil armature being in engagement with said diaphragm and urging the same in the opening direction of said differential pressure valve as a function of the energizing current flowing through said movable coil armature.

3. An improvement as defined in claim 1, including a leaf spring to which said movable coil armature is affixed for a friction-free suspension thereof.

4. An improvement as defined in claim 2, including an additional differential pressure valve connected to said fuel metering valve for maintaining the pressure differential across the fuel metering valve at a constant value determined by the pressure difference across said second differential pressure valve, said first-named differential pressure valve being connected to said additional differential pressure valve for varying the pressure difference across the latter.

5. In a fuel injection apparatus serving a spark plugignited internal combustion engine operating on fuel continuously injected into the engine suction pipe containing an arbitrarily operable butterfly valve, said apparatus being of the type that has (a) a fuel metering valve including a movable valve member disposed in the fuel line of the engine, (b) an air sensor disposed in said suction 'pipe spacedfrom said butterfly valve, said air sensor being deflected by and as a function of the air quantities flowing through said suction pipe, (0) means for exerting a return force on said air sensor, (d) means for connecting said air sensor to said movable valve member to displace the latter for metering a fuel quantity that is proportionate to the air quantities, said fuel metering being efiected at a constant pressure difference across said fuel metering valve, said pressure difference being alterable as a function of at least one engine variable, the improvement comprising A. a control valve having l a movable valve member, 2. a movable coil armature connected to said movable valve member,

3. a permanent magnet surrounding said movable coil armature, said movable coil armature and said permanent magnet forming part of a hysteresis-free electromagnetic system, and

B. conduit means connecting said fuel line at locations upstream and downstream of said fuel metering valve with said control valve for varying the flow in said conduit means as a function of the force exerted by said electromagnetic system to said movable valve member, whereby the pressure difference across said fuel metering valve is variable as a function of the intensity of the energizing current flowing through said movable coil armature. 

1. In a fuel injection apparatus serving a spark plug-ignited internal combustion engine operating on fuel continuously injected into the engine suction pipe containing an arbitrarily operable butterfly valve, said apparatus being of the type that has (a) a fuel metering valve including a movable valve member disposed in the fuel line of the engine, (b) an air sensor disposed in said suction pipe spaced from said butterfly valve, said air sensor being deflected by and as a function of the air quantities flowing through said suction pipe, (c) means for exerting a return force on said air sensor, (d) means for connecting said air sensor to said movable valve member to displace the latter for metering a fuel quantity that is proportionate to the air quantities, said fuel metering being effected at a constant pressure difference across said fuel metering valve, said pressure difference being alterable as a function of at least one engine variable, the improvement comprising a hysteresis-free electromagnetic system operatively connected to said fuel metering valve, said electromagnetic system including a permanent magnet and a movable coil armature for varying said pressure difference.
 2. An improvement as defined in claim 1, including a differential pressure valve formed as a flat seat valve having a movable valve member constituted by a diaphragm, a spring means engaging said diaphragm and urging the latter in the opening direction of said differential pressure valve, said movable coil armature being in engagement with said diaphragm and urging the same in the opening direction of said differential pressure valve as a function of the energizing current flowing through said movable coil armature.
 2. a movable coil armature connected to said movable valve member,
 3. a permanent magnet surrounding said movable coil armature, said movable coil armature and said permanent magnet forming part of a hysteresis-free electromagnetic system, and B. conduit means connecting said fuel line at locations upstream and downstream of said fuel metering valve with said control valve for varying the flow in said conduit means as a function of the force exerted by said electromagnetic system to said movable valve member, whereby The pressure difference across said fuel metering valve is variable as a function of the intensity of the energizing current flowing through said movable coil armature.
 3. An improvement as defined in claim 1, including a leaf spring to which said movable coil armature is affixed for a friction-free suspension thereof.
 4. An improvement as defined in claim 2, including an additional differential pressure valve connected to said fuel metering valve for maintaining the pressure differential across the fuel metering valve at a constant value determined by the pressure difference across said second differential pressure valve, said first-named differential pressure valve being connected to said additional differential pressure valve for varying the pressure difference across the latter.
 5. In a fuel injection apparatus serving a spark plug-ignited internal combustion engine operating on fuel continuously injected into the engine suction pipe containing an arbitrarily operable butterfly valve, said apparatus being of the type that has (a) a fuel metering valve including a movable valve member disposed in the fuel line of the engine, (b) an air sensor disposed in said suction pipe spaced from said butterfly valve, said air sensor being deflected by and as a function of the air quantities flowing through said suction pipe, (c) means for exerting a return force on said air sensor, (d) means for connecting said air sensor to said movable valve member to displace the latter for metering a fuel quantity that is proportionate to the air quantities, said fuel metering being effected at a constant pressure difference across said fuel metering valve, said pressure difference being alterable as a function of at least one engine variable, the improvement comprising A. a control valve having 